cutiepi tablet: getting internal display & HDMI to work

[Dave Stevenson]

Hi Pavel

On Tue, 12 Mar 2024 at 08:53, Pavel Machek <pavel at ucw.cz> wrote:
>
> Hi!
>
> I'm playing with CutiePi -- rip4 based tablet. I'd really like to get
> both internal display and HDMI to work at the same time, but I have
> yet to see configuration where it does.
>
> Is my impression right that I need to get xrandr / DRM based userland
> for that to work? And that needs modules not normally needed for boot?
> Would somehow have a list of those modules?
>
> Is there useful documentation somewhere?

All of the hardware for Cutie Pi is open source and documented on
either https://cutiepi.io or
https://github.com/cutiepi-io/cutiepi-doc.
On the Pi vendor kernel there is the cutiepi-panel dtoverlay to
configure their DSI panel. It doesn't disable the HDMI port(s) on the
CM4, so they should respond to hotplug.

I do have a CutiePi here, although the installation on it is pretty
old (Raspberry Pi OS Bullseye release). Updated and it's running our
5.10.74 kernel. The LCD comes up fine.

Using modetest or kmsprint, it looks like they've got the sense of the
HDMI hotplug detect line inverted. When physically disconnected,
HDMI-A-2 reports connected (but no modes as no EDID can be read), and
when connected it reports disconnected. Updating the kernel to our
current 6.6 doesn't help.

You can force the display to be active by adding eg
video=HDMI-A-2:1920x1080M at 60D to the kernel command line (easiest via
/boot/cmdline.txt). That is working for me, and I have X extending the
desktop across both screens.
Otherwise it would be a hardware mod to rework Q4 / R3062 / R18 to not
invert the HPD signal.

  Dave

> Best regards,
>                                                                 Pavel
> --
> People of Russia, stop Putin before his war on Ukraine escalates.
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